Fix gzip filename test

Author: rhpvorderman

tests/test_gzip_compliance.py

@@ -348,7 +348,8 @@ def test_metadata(self):
             self.assertEqual(cmByte, b'\x08') # deflate
 
             try:
-                expectedname = self.filename.encode('Latin-1') + b'\x00'
+                expectedname = os.path.basename(self.filename).encode(
+                    'Latin-1') + b'\x00'
                 expectedflags = b'\x08' # only the FNAME flag is set
             except UnicodeEncodeError:
                 expectedname = b''